Work continues on the precise characterization of cell types in mammalian taste buds. Although three distinct types are present their relation to function is not yet clear. Histochemical procedures now in progress may help define the interface characteristics between cells and nerves to determine whether both afferent and efferent contacts exist. A related study of taste buds of catfish barbels is aimed at characterization of cell types and relating them to function and to mammalian cell types. Trophic effects of nerves, as reflected in the pattern and time sequence of degeneration, after denervation will also be studied at the E.M. level and compared with results in mammalian buds. In addition, tracer substances such as peroxidase and H3, amino acids will be introduced both to the surface of the barbels and into the geniculate ganglion to study their penetration and movement. Bibliographic references: Murray, R.G. The ultrastructure of taste buds. Chapter 2 in: Ultrastructure of Animal Tissues and Organs, Ed. by I. Friedmann. Amsterdam: North-Holland Publ. Co. pp. 1-81, 1974. (To be presented at the Xth International Meeting of Anatomists, Tokyo, Japan.